Method of processing a pulse response with an adaptive threshold and corresponding receiver

Abstract

A method of processing a pulse response with an adaptive threshold and corresponding receiver. According to the method, an adaptive threshold is calculated that is a function of a maximum reached by the pulse response, noise, and a coefficient adjustable between 0 and 1. The processing only comes into operation for signals that exceed this threshold. Such a method may find application notably to digital radio-communications with spread spectrum.

What is claimed is:  
     
       1. A method of processing a pulse response made up of plural successive pulses overwritten with noise, comprising: 
       in a preliminary process, determining a value of a maximum amplitude of the pulses within a defined period of time and a value of a mean noise within the defined period of time;  
       calculating an adaptive threshold equal to a function of the maximum amplitude and of the mean noise;  
       comparing the pulses received with the threshold and only those pulses that exceed the threshold are taken into account to carry out processing of the signal,  
       wherein the adaptive threshold is taken to be equal to quantity B+α(M−B) where M is the value of the maximum amplitude, B is the value of the mean noise, and α is a coefficient adjustable between 0 and 1.  
     
     
       2. Method according to  claim 1 , wherein the signal to be processed is a signal corresponding to data symbols transmitted by spread spectrum, the defined period of time being equal to a duration of each symbol. 
     
     
       3. Method according to  claim 2 , wherein the processing consists of an accumulation of pulses followed by taking of a decision, the accumulation only being effective for the pulses that exceed the threshold. 
     
     
       4. Receiver for direct sequence spread spectrum radio-communications, for implementation of the method according to  claim 2 , the receiver comprising: correlation means configured to supply correlation peaks; means for processing the correlation peaks to supply signals that permit demodulation of the signal; means for accumulation and decision means for restoring a symbol of data; means for estimating the pulse response; means for calculating the maximum of the pulse response within a time interval equal to a period for the symbols; means for calculating the mean noise in this interval; a circuit to calculate an adaptive threshold, a function of the maximum and of the mean noise; a comparator with a first input connected to the means for estimating the pulse response and second input connected to the circuit for calculating the threshold, the comparator having an output that commands the accumulation means. 
     
     
       5. Receiver according to  claim 4 , wherein the circuit for calculating the adaptive threshold comprises means for calculating the quantity B+α(M−B) where M is the maximum, B is the value of the mean noise and α is a coefficient adjustable between 0 and 1.